A resist composition used in pattern forming of lithography, which constitutes a semiconductor production step, has been required to have stricter resist characteristics, in which focal depth latitude (in the following, referred to as “DOF”) is wider, line edge roughness (in the following, referred to as “LER”) of patterns is lower, and resolution is superior, as a high energy ray to be applied has become shorter in wavelength in accordance with the pattern refinement, than at the time when required in a long wavelength irradiation.
As such resist suitable for short-wavelength exposure, a chemically amplified resist composition is used. This is a pattern forming material which contains a photoacid generator that forms an acid by a high energy ray irradiation (in the following, referred to as exposure) (in the following, referred to as photoacid generator) and which forms a pattern by changing solubility in a developing solution between an exposed portion and an unexposed portion by a reaction using an acid generated by the exposure as a catalyst.
In such pattern forming material, homogeneity of resist has increasingly been regarded as a problem as practical use of extreme ultraviolet rays has approached by the progress of refinement. Until now, resists in general have been composed of a resist resin, in which solubility in a developing solution changes by action of an acid, a solvent, and a photoacid generator (as an additive) to generate the acid. However, when seeking a further refinement, such formation has been insufficient in dispersion uniformity of the resist resin and the photoacid generator. Thus, recently, there have been reports (Patent Publications 1-7) of producing a resist resin by a copolymerization of a monomer having a photoacid generation function with a monomer of a conventional resist resin raw material to incorporate the photoacid generation function into the resist resin. For example, Patent Publications 6 and 7 disclose a resist composition containing a resin prepared by polymerization or copolymerization using a methacrylic acid ester having at a side chain a triphenylsulfonium salt structure of a sulfonic acid having fluorine atoms at α-position.